Projected capacitance touch panel with reference and guard electrode

a capacitance touch panel and reference electrode technology, applied in the field of projected capacitance touch panel, to achieve the effect of improving noise immunity and reducing accuracy

Active Publication Date: 2013-10-03
SHARP KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010]This invention describes a touch panel device which overcomes the aforementioned limitations of the prior art and provides improve

Problems solved by technology

Secondly, the reference electrode and the sense electrode are designed to generate similar signals

Method used

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  • Projected capacitance touch panel with reference and guard electrode
  • Projected capacitance touch panel with reference and guard electrode
  • Projected capacitance touch panel with reference and guard electrode

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Experimental program
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Effect test

second embodiment

[0176]A limitation of the reference electrode design illustrated in FIG. 7A, FIG. 7B and FIG. 7C is that, even if noise injected from the display device couples equally to both the sense electrode and reference electrode, noise injected from the touching object may not. For example, depending on the location and size of the touching object, the ratio of the parasitic capacitances formed between the object and the sense and reference electrodes (COS, COR) may not be the same as the ratio of the parasitic capacitances formed between the display device and the sense and reference electrodes (CDS, CDR), i.e. COS / COR≠CDS / COR. Further, if the areas of the sense and reference electrodes are weighted such that CDS=β.CDR then any difference in the injected noise will be multiplied by the weighting factor β in the sense circuit. Accordingly, in a touch panel device in accordance with the invention, sense and reference electrodes with improved noise immunity are provided. FIG. 11A shows an exe...

fourth embodiment

[0179]However, even though it is now only the difference between the first and second mutual coupling capacitors 105, 106 that is being measured, saturation may still occur in the sensing circuit if the baseline capacitance (i.e. the capacitance when no touching object is in the proximity of the touch panel) of the first and second mutual capacitors is significantly different—for example when the difference in baseline capacitance is similar to the maximum difference that is expected to be caused by a touching object. Although one solution to this problem is to account for this baseline by increasing the range of capacitances that may be measured, this is undesirable since it must be done by reducing the sensitivity of the sensing circuit and hence reducing the SNR. In accordance with the invention, the sense electrode and reference electrode are additionally arranged such that the baseline value of the mutual capacitance between the drive electrode and sense electrode is substantia...

fifth embodiment

[0180]In accordance with the invention, the most general embodiment of a second aspect of the invention, a mutual capacitance type touch panel device includes an electrode array comprising at least one each of a drive electrode, and a pair of matched sense electrodes. FIG. 14A shows an exemplary arrangement of the electrode array 400 with drive electrode 401 and sense electrode pair 402 which comprises a first dual-function electrode 403 and a second dual-function electrode 404. The first and second dual-function electrodes 403, 404 are arranged substantially symmetrically around each drive electrode such that the first (or second) dual-function electrode is adjacent to the drive electrode whilst the second (or first) dual-function electrode is separated from the drive electrode by the first (or second) dual-function electrode. As used herein, the term “symmetrical” refers to symmetry relative to at least one axis. The drive electrode 401 therefore forms a first mutual coupling capa...

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Abstract

A mutual capacitance touch panel device includes a substrate, and an array of electrode elements formed on the substrate. Each electrode element includes a drive electrode, a sense electrode and a reference electrode, the reference electrode arranged between the drive electrode and the sense electrode. A first mutual coupling capacitance is formed between the drive electrode and the reference electrode of each electrode element, wherein the drive electrode and reference electrode are configured such that the first mutual coupling capacitance is substantially insensitive to an object touching the surface of the touch panel.

Description

TECHNICAL FIELD[0001]The present invention relates to touch panel and display devices. In particular, this invention relates to projected capacitance touch panels integrated with liquid crystal display (LCD) devices. Such an LCD device with integrated touch panel may find application in a range of consumer electronic products including, for example, mobile phones, tablet and desktop PCs, electronic book readers and digital signage products.BACKGROUND ART[0002]Touch panels have recently become widely adopted as the input device for high-end portable electronic products such as smart-phones and tablet PCs. Although, a number of different technologies can be used to create these touch panels, capacitive systems have proven to be the most popular due to their accuracy, durability and ability to detect touch input events with little or no activation force.[0003]The most basic method of capacitive sensing for touch panels is demonstrated in surface capacitive type touch panels (also known...

Claims

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Application Information

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IPC IPC(8): G06F3/044H01H65/00
CPCY10T29/49105G06F3/044G06F3/04182G06F3/0443G06F3/0446G06F3/0448
Inventor BROWN, CHRISTOPHER JAMESCOULSON, MICHAEL PAUL
Owner SHARP KK
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